Biomedical subjects

J Tzoutzas

Publications and source records attributed to J Tzoutzas.

10 recordsLinked to original sources

PubMed2004

The effect of sterilization methods on the light transmission characteristics and structure of light-curing tips.

The purpose of this study was to investigate the effect of various sterilization methods on the light transmission and the structural characteristics of two light-curing tips. Twenty tips from two light-curing devices [Elipar II (EL) and Heliolux II (HL)] were classified into four groups. The tips in groups A to C were subjected to sterilization with 0.2% sodium dichloroisacyanurate solution (Presept), 2% glutaraldehyde solution (Cidex) (2 h cycle(-1)) and water-steam autoclave (120 degrees C, 1 bar, 12 min cycle(-1)), respectively. A total of 2100 sterilization cycles was performed for all methods tested. The transmitted light intensity (TLI) was measured at specific sterilization time intervals by a curing radiometer (Model 100, Demetron). The final % TLI reduction of the sterilized tips was calculated relative to the corresponding control ones. The topography and composition of the front curing tip surfaces were determined using scanning electron microscopy combined with electron probe microanalyser. Autoclaving caused the lowest final TLI decrease (EL: 15%, HL: 19%) compared with Presept (EL: 60%, HL: 42%) and with Cidex (EL: 68%, HL: 52%). Cidex yielded higher TLI drop than Presept for both types of tips examined. Elipar tips were found to be more sensitive than Heliolux tips to both chemical sterilization techniques. Total or partial coating of the tip surfaces with insoluble salts after sterilization with Presept and Cidex was detected, mainly composed of Ca, Cl, Al, Pd and Mg traces. No changes were noted on the surfaces after autoclave. Water-steam autoclave is safer than the 0.2% sodium dicloroisocyanorate and 2% glutaraldehyde chemical sterilization agents regarding the light transmission characteristics and the structure of the light-curing tips.

Dental Disinfectants↗

PubMed1997

Effect of topical fluoride agents on the morphologic characteristics and composition of resin composite restorative materials.

STATEMENT OF PROBLEM: The high reactivity of fluoride agents used in topical fluoride treatments have raised important questions on their potential adverse effects on restorative materials. PURPOSE: The purpose of this study was to evaluate the effect of topical fluoride agents used for office or home treatments on the surface morphologic characteristics and composition of composite restoratives. MATERIAL AND METHODS: The fluorides used were Act, Phosflur, Gel II, Prevident, Stop, Butler APE, Nupro, and Omni Gel & Rinse. The composites tested were Brilliant DI, Heliomolar Ro, Herculite XRV, and P-50. The pH of the fluorides was measured as received and after dilution with water at a 1:3 volume ratio. The composites were subjected to the fluoride treatments until the total number of applications simulated the equivalent of 4 years under treatment. The changes induced on the surface morphologic features and composition of the restoratives were assessed by multiple internal reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray microanalysis. RESULTS: All fluorides showed an acidic pH that was not significantly changed after dilution, except Stop, which exhibited a significant pH reduction. All fluorides increased the amount of loosely bound water in the composite matrix. Butler APF gel was the most aggressive for Brilliant DI and Herculite XRV, leading to excessive surface degradation, porosity, destruction of the filler-matrix interface, filler dissolution, and debonding. A reduction in the extent of remaining C = C bonds was observed in Herculite XRV after Butler APF treatment; Phosflur, Gel II, and Prevident had a milder effect. Treatment of Brilliant Dl and Herculite XRV with Omni Gel & Rinse resulted in the formation of a stable precipitation layer rich in barium, phosphorus, tin, oxygen, and fluoride. P-50 was severely affected at the resin-matrix interface after Stop treatment, whereas Omni Gel & Rinse induced fewer surface changes. Heliomolar Ro was the least affected restorative regardless of the type of fluoride used.

Acidulated Phosphate Fluoride↗

PubMed1990

[Microleakage pattern around posterior composite resin restorations, combined with a ceramometallic cement (sandwich technique)].

The purpose of this in vitro investigation was to examine the degree of microleakage in class II, MOD, posterior composite resin restorations, in the distal wall of which a layer of 1,5 mm of ceramometallic cement was condensed. Conventional MOD cavities were prepared using 330 and 56 tungsten carbide burs in 20 premolars extracted for orthodontic reasons. In the first group (10 specimens) the gingival floor was located in the enamel, above the cementoenamel junction and in the second group the gingival floor was located below the CEJ. In the mesial box, cervically, a layer of 1,5 mm of ceramometallic cement (Ketac Silver) was condensed and etched with orthophosphoric acid 37%, the cavity was filled with posterior composite resin (Heliomolar, Vivadent) and 24 hours later the specimens were polished using Sof-Lex discs and thermocycled between 4 degrees C and 60 degrees C for 50 cycles of 2 minutes each. The specimens were immersed for 2 hours in 2% basic fuchsin solution, washed, cleaned with acetate solution and split in two halves longitudinally in a mesiodistal direction, using a hard tissue microtome. From the detection of the degree of dye penetration we conclude that: a) In the cervical walls located in cementum, where cermet cement was condensed, minimal dye penetration was detected b) In the opposite side, where the composite resin existed on dentin-cementum, the dye penetration is more severe c) Dye penetration in cavities located in the enamel, is moderate in the areas where cermet cement existed d) No dye was detected in the interface between cermet cement and posterior composite, in most specimens.

Bicuspid↗

PubMed1989

[Effect of bonding agents in the degree of microleakage around posterior composite resin restorations].

The purpose of this in vitro study was to examine, by the dye technique, the microleakage pattern of two posterior composite resin materials, alone or combined with three commercially available dentin bonding agents. Composite resins used were P-30 (3M) and Heliomolar (Vivadent). The bonding agents were Gluma (Bayer), Scotch-bond LC (3M) and Dentin Adhesit (Vivadent). MOD cavities were prepared on extracted posterior teeth with a 330 tungsten carbide bur, in an airtor handpiece. The gingival floor of the mesial surface was located in the enamel above the CEJ and the distal gingival floor in the cementum below the CEJ. Specimens were thermocycled between 4 degrees and 60 degrees C for fifty cycles of two minutes each and imbibed for 10 hours in a 2% basic fuchsin solution and split in two halves. According to the results we obtained we came to the conclusion that: Both composite resins exhibited significant microleakage when they were used alone, without bonding agent. The gingival floor of the mesial surface (located in the enamel) exhibited in most specimens, less microleakage than the distal one. The use of bonding agents decreased but not eliminated the microleakage at the gingival floor of the cavities.

Composite Resins↗

PubMed1989

[In vitro study of the microleakage pattern around posterior composite resin restorations using a new dentin bonding agent].

A totally new product, by the name Scotchbond 2 (3M Co) appeared recently in the field of bonding agents. Grace to its improved formula, the manufacturers claim that both the bond strength and the sealing ability of the material, render it trustful for use in both anterior and posterior composite resin restorations. The purpose of this in vitro investigation was to determine the microleakage pattern around slot type cavities, restored with posterior composite resin (P-50, 3M Co) using two different generations of bonding agents. Two types of cavities were prepared in sound premolars extracted for orthodontic reasons. In the first group (10 teeth) the cervical wall was located in the enamel, above the cementoenamel junction and in the second group (10 teeth) the cervical wall was located below the CEJ. The enamel surrounding the cavity margins was etched using 37% orthophosphoric acid gel, rinsed and dried and the bonding agents were applied and cured according to the manufacturer s instructions. The posterior composite was condensed and light-cured incrementally, in three horizontal layers. The samples were thermocycled for 200 cycles of 4 minutes each between 4.37 and 60 degrees centigrade, covered with fingernail varnish and sticky wax and immersed in 0.5% basic fuchsin dye for 12 hours. The specimens were split in two halves longitudinally in a mesiodistal direction in a hard tissues microtome and the degree of dye penetration was evaluated using an optical microscope. According to the results obtained we come to the conclusions that: 1. The use of Scotchbond 2 minimized but did not eliminate the microleakage around posterior composite resin restorations, in both types of cavities.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicuspid↗

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